Electrodeposition of metals.



A. G. BETTS.

ELECTRODEPOSITION 0F METALS.

APPLICATION FILED MAY 15- I916.

Patented Jan. 8, 1918.

caries.

ANSON Gr. IBETTS, OF ASHEVILLE, NORTH CAROLINA.

ELEGTRODEPOSITION 0F METALS.

Specification of Letters Patent.

Patented Jams, 1918.

' Application filed May 15, 1916. Serial No. 97,544.

To all whom it may concern:

Be it known that I, ANsoN G. Bn'rrs, a citizen of the United States,residing at Asheville, in'the county of Buncombe and State of NorthCarolina, have invented certain new and useful Improvements inElectrodeposition of Metals, of which the following is a full, clear,and exact description.

This inventionrelates to the electrolytic recovery of metals fromsoluti0ns,of salts thereof, particularly zinc from acid sulfatesolutions. In the electrolyticmethod of zinc recovery the zinc sulfateis electrolyzed with suitable anodes;-and cathodes, with deposit ofmetallic zinc on the cathodes, thus liberating sulfuric acid and makingthe electrolyte more acid until it is finally removed from theelectrolytic cell as a solution of sulfuric acid containing only alittle zinc sulfate. i Y

It is well known that the ambunt of zinc deposited for a givenconsumption of current is always considerably less than the amount thatwould be expected from theoretical considerations. In short, theefficiency of the process is undesirably low, and hence the costundesirably high. It isaccordingly the object of my present invention toprovide an electrolytic process by which the amount of zinc depositedwith iven current consumption will be increased.

nother object is to diminish the amount of hydrogen liberated along withthe zinc at the'cathode. These objects I attain by the simple expedientof giving the inner surface of the electrolytic tank, in contact withthe solution, (which surface is usually metallic lead), an electricpotential of its own, relative to the solution, so thatsome currentwillflow from the solution to the tank as well as to the cathode: Thishas the effect of increasing the efliciency'of the cell, that is, itpermits the use of less current for a given amount of zinc deposited,or, conversely, permits more zinc to be deposited with the same amountof current.

It is my present belief that the abovementioned potential (which forconvenience can be referred to as the tank potential) accomplishes theresult described by (1) opposing the formation of a lead salt, more orless soluble in the zinc solution, by the acid of the zinc solutionattacking the lead surface of the tank, Whichsalt,'when present in thesolution, exerts an unfavorable efiect, probably catalytic, upon thedeposition of the zinc; (2) diminishing the amount of hydrogen liberatedat the cathode along with the zinc, which hydrogen tends to cling to thecathode and thereby increase the resistance of the cell, causing some ofthe current to be wasted in heating effects; and (3) hinderingre-dissolving of zinc from thercathode by the free acid of the solution,that is, hindering re-formation of the zinc salt by attack of the freeacid upon the metallic zinc deposited on the cathode.

In the accompanying drawing I have shown diagrammatically a simpleelectrolytic cell for practising my method in the preferred manner. Inthe cell illustrated, 1 is the tank, which may be made of wood, 2 isthe'lead lining, and 3 designates the electrolyte, preferably an acidzinc sulfate solution. The anode and cathode are designated A and Crespectiyely, and may be of any suitable material, for example aluminum.The cathode is electrically connected to the lead lining by wire 4. Thisgives the lead surface a negative potential with respect to the anode orpositive electrode A, with the result that current flows to the lead andthence to the negative pole as well as direct to the latter. This hasthe effect, in general, of opposing the formation of a lead salt, whicheffect may possibly be explained on the theory that as fast as the leadsalt is formed it is reducedby electrolytic action and the leadre-deposited on the lead surface. It also tends to deposit zinc on thelead surface, and if enough current were allowed to flow to the lead theamount of zinc there deposited would be considerable. I therefore preferto include a suitable resistance R'in the connection, of such valuethat" sufficient current can HOW to prevent formation of lead salt. Thecurrent ma even be large enough to deposit a smal amount of zinc onthelead surface,but such deposit can easily be removed from time to timeby means of sulfuric acid solution.

' It is to be understood that the invention 1s not limited tothespecific details herein described but can be practised in other ways"without departure from its spirit. Nor is the invention limitedto zincrecovery, but is in general applicable to other metals that are moresoluble in the acid electrolyte used than is the metal (for examplelead) used for the inner surface of the tank.

I claim:

1. The method of electrodepositing metals of greater solubility in theacid of the salt contained in the electrolyte than lead, comprising thestep of electrolyzing a solution of a salt of the metalwith suitableanode and cathode in a vessel having an inner surface of lead whilepassing current to the lead inner surface.

'2. The method of electrodepositing metals of greater solubilit in theacid of the salt contained in the-e ectrolyte than lead, comprising thestep of electrolyzing a solution of a salt of the metal with suitableanode and cathode in a vessel having an inner surface of lead, whilepassing current from the anode to the said lead innerjsurface of thevessel.

3.. The method of electrodepositing metal in a vessel having a leadinner surface, comprising electrolyzing in such vessel a solution of asalt of the metal While maintaining at the said lead. surface a negativepotential high enough to substantially prevent the formation of a leadsalt thereat.

4. The method of electrodepositing zinc from its sulfate solutions,comprising electrolyzing the solution with suitable anode and cathode ina vessel having a lead inner surface, While passing current from theelectrolyte to the said lead inner surface.

5. An apparatus for electrodeposition comprising a lead linedreceptacle, an anode and a cathode therein, each spaced from saidreceptacle, a positive terminal connected to said anode and a negativeterminal con- .nected to said cathode; and an independent connectionbetween the lead lining of said receptacle and the said negativeterminal, said independent connection offering a relativel electriccurrent.

In testimony whereof I hereunto affix my signature. v

ANSON G. BETTS.

high resistance to the flow-of the.

